This invention relates to an apparatus for boring or tunneling underground using an earth boring, drilling, or tunneling machine. In particular, the invention relates to a laser positioning system for measuring the position pipe casing or bore forming machinery as it is as it is pushed and steered through the earth so that a more accurate line and grade of the bore or tunnel may be had.
Prior earth boring machines are known which are slidably mounted and reciprocated longitudinally along a track by means of a hydraulic piston assembly. The forward end of the boring machine rotatably mounts an auger which is rotated within the interior of the pipe casings with the forward end of the auger boring a hole in the earth. The auger bores the hole and carries the dirt outwardly for ejection at the boring machine. The hydraulic pistons are forced on the boring machine to drive the pipe casings through the bore as it is formed. Successive pipe casings are attached to the string of pipe casings as the bore progresses. A steering head is typically located at the forward pipe casing and is provided with a directional control device. Typical earth boring machines are disclosed in U.S. Pat. Nos. 4,042,046; 4,013,134; and 4,438,820. U.S. Pat. No. 4,042,046 discloses an earth boring machine having a double jointed steering head so that its direction may be controlled in both the vertical and horizontal planes. The system does not have an entirely reliable means for measuring the position of the cutting head in both the horizontal and vertical planes so that it may be steered accurately. U.S. Pat. Nos. 4,042,046 and 4,013,134 utilize a conventional water level to determine the grade of the casing. That type of device includes a sight tube on an indicator board at the boring pit station connected to a water line affixed to the top of the casing being bored and pushed through the ground. Any deviation in the leading edge of the casing from the desired grade either up or down provides a corresponding response to the water level in the sight tube at the boring pit. Based on the readings of the sight tube, the operator in the boring pit may pivot the steering head of the casing in the vertical plane by means of a mechanical linkage. However, the water line connected to the sight must be vented on both ends. If the device is used below the water table, water can enter the tube and interfere with the reading of the sight tube. The water level devices also have inherent vibration problems which necessitate that the apparatus be shut down to take a reading of the sight tube. The sight tube cannot be monitored simultaneously with the boring operation. With the vibrations, air locks are often created which interfere with the accuracy of the reading in the sight tube. The above inaccuracies can result in the final line being off grade which often requires re-boring. U.S. Pat. No. 4,438,820 proposes an improved rate sensor for eliminating the problems utilized in water level sensors. However, the problem remains that the prior art earth boring and tunneling machines do not recognize the ability to provide means for accurately measuring the position of the steering or cutting head.
U.S. Pat. No. 5,133,418, discloses a directional drilling system with an eccentric mounted motor and biaxial position sensor for steering a drilling string forming a bore underground. This system has been found advantageous for many applications, particularly where a rotating drill string is used. The position and measuring system relies heavily on electronics including an angular rate sensor and encoder which operate with an eccentric mounted drilling head to not only measure the position of the drill string, but also the rotational position of the eccentrically mounted drilling head.
U.S. Pat. No. 5,099,927 discloses an apparatus for guiding and steering an earth boring casing. This application also utilizes a positioning measuring system that includes a pair of angular rate sensors whose sensing axes are rotated 90 degrees with respect to each other, and also relies heavily on electronics.
U.S. Pat. No. 4,656,743 discloses an arrangement for determining the position of a hollow section system which is pushed forward which comprises measuring apparatus arranged one behind the other in the hollow section system. However, the light sources and detectors are located in the apparatus such that optical systems must be employed for beam direction. This renders the apparatus high susceptible to misalignment when used in this rather harsh environment of underground boring or pipe pushing.
Accordingly, an object of the invention is to provide a highly accurate and reliable positioning measuring system for guiding an earth boring apparatus
Another object of the present invention is to provide an improved position measuring system for an earth boring apparatus utilized to form underground bores such as tunneling machines, pipe pushing machines, direction drilling machines, and the like.
Another object of the present invention is to provide an improved measuring system for guiding and steering an earth boring apparatus which minimizes the amount of electronics that are used.
Another object of the invention is to provide a highly accurate and reliable laser positioning measuring system for measuring the position and guiding an earth boring apparatus while being steered to form an underground bore.